<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    
class Father{
constructor(x,y) {
this.x = x;
this.y =y
}
sum(x,y) {
 console.log( this.x+this.y);
}
}
class Son extends Father {
  constructor(x,y) {
    super(x,y)
  } 
  sub(x,y) {
    console.log(this.x-this.y);
  }
}
let son1 = new Son(10,5)
son1.sum()
son1.sub()
</script>
</html>